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NY CDL Doubles and Triples study materials
NY CDL Doubles and Triples study resources

NY CDL Doubles and Triples practice questions

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Question 1Coupling and Uncoupling

Before backing a tractor under a semitrailer to couple, what should you check first?

  1. That the trailer landing gear is raised
  2. That the fifth wheel is fully greased
  3. That the trailer lights are switched on
  4. That the trailer wheels are chocked or the spring brakes are set Correct answer.

Explanation

A trailer that can roll while you are coupling can crush you or slide off the kingpin. Chock the wheels or confirm the spring brakes are applied before the tractor moves under the trailer.

Question 2Coupling and Uncoupling

When backing the tractor toward the trailer during coupling, the trailer kingpin should end up where?

  1. Over the drive axle housing
  2. Centered in the fifth wheel throat Correct answer.
  3. Slightly ahead of the fifth wheel throat
  4. Just behind the fifth wheel jaws

Explanation

The kingpin must enter the throat of the fifth wheel squarely so the jaws can close around it. Misalignment causes the pin to hit the fifth wheel body instead of locking in.

Question 3Coupling and Uncoupling

After the fifth wheel jaws close on the kingpin, how do you confirm the coupling is locked?

  1. Watch the trailer lights for a signal
  2. Pull the release handle and watch the jaws
  3. Tug test in a low gear with the trailer brakes released Correct answer.
  4. Listen for the engine to change pitch

Explanation

A tug test with the trailer brakes released and the tractor in a low gear confirms the jaws are holding the kingpin. If the coupling is not locked, the trailer will not move with the tractor.

Question 4Coupling and Uncoupling

Why is a visual check under the trailer important after coupling?

  1. It checks the trailer mud flaps
  2. It verifies the air lines are connected
  3. It confirms the jaws are closed around the kingpin Correct answer.
  4. It shows the landing gear is still down

Explanation

Looking under the trailer lets you see the fifth wheel jaws wrapped around the kingpin and the release handle in the locked position. A tug test alone may not reveal a partially closed jaw.

Question 5Coupling and Uncoupling

What should you do with the trailer air supply (red) knob before backing under the trailer to couple?

  1. Cycle it repeatedly
  2. Push it in so the trailer spring brakes stay applied Correct answer.
  3. Leave it in any position
  4. Pull it out to supply air to the trailer

Explanation

With the red knob pushed in, the tractor does not supply air, so the trailer spring brakes remain applied and hold the trailer still. This keeps the trailer from rolling during coupling.

Question 6Coupling and Uncoupling

When uncoupling, what is the correct order for the first steps?

  1. Lower the landing gear, then pull the air lines Correct answer.
  2. Release the fifth wheel, then lower the landing gear
  3. Pull the air lines, then lower the landing gear
  4. Raise the landing gear, then release the fifth wheel

Explanation

Lower the landing gear to support the trailer before disconnecting anything else. Then disconnect the air lines and electrical cord so the trailer is stable and the lines are clear.

Question 7Coupling and Uncoupling

What is the purpose of the glad hands on a doubles or triples combination?

  1. To connect the trailer air lines to the tractor or dolly Correct answer.
  2. To lock the fifth wheel jaws
  3. To hold the electrical cord in place
  4. To secure the landing gear crank

Explanation

Glad hands are the couplers that join the tractor and trailer (or dolly) air lines. They must be seated and sealed so the brakes and suspension receive air.

Question 8Coupling and Uncoupling

When connecting glad hands, which color is normally the emergency (supply) line?

  1. Blue
  2. Green
  3. Red Correct answer.
  4. Black

Explanation

The emergency or supply line is normally red, and the service line is normally blue. Matching colors helps ensure the lines are not crossed.

Question 9Coupling and Uncoupling

What should you do if the glad hands will not seal and air leaks at the connection?

  1. Increase engine RPM to overcome the leak
  2. Tape the coupler and continue
  3. Inspect the seals and couplers, then reconnect or replace the seals Correct answer.
  4. Wrap the lines together with cord

Explanation

Leaking glad hands usually mean worn or missing seals or damaged couplers. Inspect and replace the seals or repair the couplers so the connection seals properly.

Question 10Coupling and Uncoupling

When coupling a set of doubles, where does the dolly connect?

  1. Behind the last trailer
  2. Between the first and second trailers Correct answer.
  3. Between the tractor and the first trailer
  4. On the tractor frame behind the cab

Explanation

In a doubles combination the dolly sits between the first and second trailers, carrying the converter gear and a fifth wheel for the second trailer. It is not placed ahead of the first trailer.

Question 11Coupling and Uncoupling

What feature on a dolly allows it to be coupled to the first trailer?

  1. Only a set of glad hands
  2. A pintle hook
  3. A set of landing gear
  4. A kingpin and a fifth wheel Correct answer.

Explanation

A dolly has a kingpin that locks into the first trailer's rear fifth wheel and its own fifth wheel to accept the second trailer's kingpin. This lets it act as a bridge between the two trailers.

Question 12Coupling and Uncoupling

Before coupling a dolly to the rear of the first trailer, what must be done with the dolly?

  1. Remove its fifth wheel
  2. Chock its wheels or set its spring brakes and align its kingpin Correct answer.
  3. Raise its landing gear fully
  4. Disconnect its air lines

Explanation

The dolly must be held still and its kingpin aligned with the rear fifth wheel of the first trailer. Chocking or setting the spring brakes keeps it from rolling during coupling.

Question 13Coupling and Uncoupling

What is the purpose of the converter dolly's air tank?

  1. To cool the dolly tires
  2. To supply air for the dolly and second trailer brakes Correct answer.
  3. To store fuel for the dolly engine
  4. To power the trailer lights

Explanation

The dolly air tank stores compressed air so the dolly and the trailer it carries have a reserve for braking. It is part of the air brake system, not a fuel or lighting component.

Question 14Coupling and Uncoupling

When uncoupling a set of doubles, which trailer should normally be uncoupled first?

  1. The first trailer from the tractor
  2. The rear trailer from the dolly Correct answer.
  3. The dolly from the first trailer
  4. All connections at once

Explanation

The rear trailer is normally dropped first, then the dolly, then the first trailer from the tractor. Working from the rear forward keeps the combination stable as each unit is removed.

Question 15Coupling and Uncoupling

Before lowering the landing gear on a trailer you are about to uncouple, what should you confirm?

  1. The fifth wheel is greased
  2. The trailer lights are off
  3. The glad hands are already disconnected
  4. The trailer is on level ground and the tractor brakes are set Correct answer.

Explanation

The trailer should be on firm, level ground and the tractor brakes set so nothing moves while you work. This prevents the trailer from rolling or the tractor from shifting during uncoupling.

Question 16Coupling and Uncoupling

What is the correct way to test that the fifth wheel release handle is fully locked after coupling?

  1. Push the handle sideways
  2. Pull the handle outward and leave it out
  3. Remove the handle
  4. Check that the handle is in and the safety latch is engaged Correct answer.

Explanation

The release handle should be pushed in with its safety latch engaged so the jaws cannot open. A handle left out means the lock is not secured.

Question 17Coupling and Uncoupling

Why should you avoid backing under a trailer at an angle when coupling?

  1. It makes the trailer lights flicker
  2. It can damage the fifth wheel and prevent the jaws from locking Correct answer.
  3. It increases fuel consumption
  4. It causes the landing gear to rise

Explanation

Backing at an angle can bend the fifth wheel, damage the kingpin area, and keep the jaws from closing squarely. Approach straight so the kingpin enters the throat centered.

Question 18Coupling and Uncoupling

After coupling and raising the landing gear, what should you do with the trailer air supply knob?

  1. Pull it out to charge the trailer system and release the spring brakes Correct answer.
  2. Cycle it five times
  3. Remove it
  4. Leave it pushed in

Explanation

Pulling the red knob out supplies air to the trailer, charging the system and releasing the spring brakes so the trailer can roll. This step follows coupling and raising the landing gear.

Question 19Coupling and Uncoupling

What does the term "converter gear" refer to in a doubles combination?

  1. The landing gear crank
  2. The dolly that converts a single trailer into a doubles set Correct answer.
  3. The gear ratio in the tractor transmission
  4. The electrical converter for trailer lights

Explanation

Converter gear, or converter dolly, is the axle assembly that couples behind the first trailer and carries the second. It converts a tractor-trailer into a doubles combination.

Question 20Coupling and Uncoupling

During a tug test on a doubles combination, the tractor moves but the rear trailer stays put. What does this most likely indicate?

  1. The front trailer lights are burned out
  2. The dolly tires are overinflated
  3. The tractor engine is low on oil
  4. The rear trailer brakes are still applied or its coupling is not locked Correct answer.

Explanation

If the tractor moves and the rear trailer does not follow, either its spring brakes are still set or the coupling to the dolly is not locked. Both conditions must be corrected before driving.

Question 21Coupling and Uncoupling

What is the safest way to check that a dolly's spring brakes are released before towing?

  1. Pull the red knob out and check that the dolly wheels roll freely Correct answer.
  2. Push the red knob in and listen
  3. Raise the dolly landing gear
  4. Disconnect the glad hands

Explanation

Pulling the red knob out supplies air and releases the spring brakes. Confirming the dolly wheels roll freely shows the brakes are released before you tow.

Question 22Coupling and Uncoupling

Why must the trailer be at the correct height before the tractor backs under it to couple?

  1. So the landing gear can be removed
  2. So the kingpin enters the fifth wheel at the proper level Correct answer.
  3. So the glad hands reach the ground
  4. So the trailer lights align

Explanation

The trailer nose must be set so the kingpin slides into the fifth wheel throat without hitting the plate or riding too high. Correct height prevents damage and ensures a solid lock.

Question 23Coupling and Uncoupling

When uncoupling, why should you pull the tractor forward slightly after releasing the fifth wheel?

  1. To test the trailer lights
  2. To let the trailer settle onto its landing gear and clear the kingpin Correct answer.
  3. To reset the dolly brakes
  4. To charge the trailer air system

Explanation

Pulling forward after release lets the trailer settle onto the landing gear and moves the tractor clear of the kingpin. This confirms the trailer is supported before you disconnect the lines.

Question 24Coupling and Uncoupling

You are coupling a second trailer to a dolly and the jaws will not close. What is the most likely cause?

  1. The dolly air tank is full
  2. The trailer is too light
  3. The electrical cord is connected
  4. The kingpin is not aligned with the dolly fifth wheel throat Correct answer.

Explanation

Jaws that will not close usually mean the kingpin is not centered in the throat or the trailer height is wrong. Realign the kingpin and reset the height before trying again.

Question 25Coupling and Uncoupling

What should you do with the electrical cord when uncoupling a trailer?

  1. Disconnect it and secure it so it does not drag Correct answer.
  2. Coil it around the landing gear
  3. Leave it connected until the tractor is driven away
  4. Cut it if it is stuck

Explanation

The electrical cord should be disconnected and secured out of the way so it is not dragged or damaged. Leaving it connected while driving away would tear it loose.

Question 26Coupling and Uncoupling

In a doubles or triples combination, what keeps the converter dolly's fifth wheel from tipping when the dolly is not carrying a trailer?

  1. The dolly air tank pressure holding it upright
  2. A safety chain hooked to the lead trailer frame
  3. A locking lever that secures the fifth wheel in a level position Correct answer.
  4. A spring-loaded latch pin that drops into the fifth wheel plate

Explanation

Converter dollies have a locking mechanism that holds the fifth wheel level and prevents it from tipping up when no trailer is resting on it. The fifth wheel must be locked in the level position before the dolly is towed or backed under a trailer. Failing to lock it can let the plate flip and damage the dolly or make coupling impossible.

Question 27Coupling and Uncoupling

You are preparing to back the tractor under the lead trailer of a doubles set. What is the correct position of the trailer apron and kingpin relative to the fifth wheel?

  1. The trailer floor should be slightly lower than the fifth wheel so the tractor lifts it
  2. The trailer should be low enough that the kingpin contacts the fifth wheel plate
  3. The trailer should be high enough that the fifth wheel passes under the apron without striking it Correct answer.
  4. The trailer height does not matter as long as the landing gear is down

Explanation

The trailer must sit high enough that the tractor's fifth wheel slides under the apron and the kingpin enters the throat of the fifth wheel. If the trailer is too low, the tractor will strike the trailer or the kingpin will hit the fifth wheel plate instead of locking. If it is too high, the kingpin may pass over the fifth wheel entirely.

Question 28Coupling and Uncoupling

After you have coupled the tractor to the lead trailer, what is the correct sequence for the tug test on a doubles combination?

  1. Raise the landing gear first, then pull forward to test the coupling
  2. Set the trailer brakes, release the tractor brake, pull gently against the trailer brakes, then check for a gap Correct answer.
  3. Pull forward at highway speed and apply the trailer brakes to feel for slack
  4. Release the parking brake, pull forward firmly, then set the brake and check the gap

Explanation

The tug test is performed by setting the trailer spring brakes and pulling gently against them with the tractor. If the fifth wheel jaws are not locked, the trailer will separate and a gap will appear between the tractor and trailer. The test is done at low speed with the trailer brakes holding, not at highway speed.

Question 29Coupling and Uncoupling

When uncoupling a set of doubles, why should the dolly be disconnected from the lead trailer before the lead trailer is moved away?

  1. The dolly must be supported and its air lines disconnected while the lead trailer is still stationary Correct answer.
  2. The dolly brakes will not release once the lead trailer moves
  3. The dolly can be towed behind the tractor to the next trailer
  4. The lead trailer cannot move with a dolly attached

Explanation

The dolly must be uncoupled from the lead trailer while that trailer is stationary and supported, because the dolly has no landing gear of its own and must be secured before the trailer is pulled away. Air lines and the electrical cord between the lead trailer and dolly must be disconnected first. Moving the lead trailer with the dolly attached is not the normal uncoupling procedure.

Question 30Coupling and Uncoupling

What is the purpose of the shut-off valves (quarter-turn valves) at the glad hand connections on a doubles combination?

  1. They lock the glad hands together to prevent separation
  2. They allow air lines to be closed off so the system can be charged or serviced without losing air Correct answer.
  3. They prevent moisture from entering the trailer air system
  4. They regulate the air pressure delivered to the trailer brakes

Explanation

Shut-off valves let you close individual air lines so the rest of the system can be charged or serviced without losing air pressure. They are also used to isolate a leaking line or trailer. They do not regulate pressure, dry the air, or mechanically lock the glad hands.

Question 31Coupling and Uncoupling

You are coupling a second trailer to a converter dolly. After backing under and locking the fifth wheel, what should you do before raising the second trailer's landing gear?

  1. Disconnect the lead trailer's air lines
  2. Connect the air lines and electrical cord, then perform a tug test Correct answer.
  3. Lower the dolly's landing gear
  4. Release the dolly's spring brakes and pull forward

Explanation

After the fifth wheel locks on the second trailer, the air lines and electrical cord must be connected and the coupling verified with a tug test before the landing gear is raised. Raising the gear before confirming the coupling could drop the trailer. The dolly has no landing gear to lower, and disconnecting the lead trailer's lines would defeat the purpose.

Question 32Coupling and Uncoupling

During a pre-trip inspection of a doubles combination, you notice the dolly's air tank has a drain valve. What is the correct procedure for this valve?

  1. Leave it open so condensation drains continuously
  2. Drain it during the pre-trip inspection to remove moisture and close it before driving Correct answer.
  3. Close it permanently because the air dryer handles all moisture
  4. Open it only when the dolly is uncoupled and the brakes are released

Explanation

Air tanks, including the dolly's tank, collect moisture and must be drained during the pre-trip inspection. The valve is opened to blow out any accumulated water and then closed before the vehicle is driven. Leaving it open would prevent the air system from building pressure.

Question 33Coupling and Uncoupling

When backing the tractor under the lead trailer of a doubles set, at what point should you stop and check the coupling?

  1. After you have pulled the tractor forward several feet
  2. After you have raised the landing gear
  3. After the fifth wheel jaws close and you hear the lock engage, before pulling forward Correct answer.
  4. As soon as the kingpin touches the fifth wheel plate

Explanation

You stop when the fifth wheel jaws have closed around the kingpin and the locking mechanism engages. At that point you check that the jaws are locked and the release handle is in the locked position before performing the tug test. Stopping earlier means the kingpin is not captured; pulling forward first risks an uncoupled trailer.

Question 34Coupling and Uncoupling

What is the correct way to handle the electrical cord between the lead trailer and the converter dolly during uncoupling?

  1. Disconnect it and secure it so it does not drag or contact the ground Correct answer.
  2. Cut the cord if it will not release
  3. Coil it around the dolly's fifth wheel handle
  4. Leave it connected so the dolly lights stay on during separation

Explanation

The electrical cord must be disconnected and secured so it does not drag on the ground or get caught between the vehicles during separation. A dragging cord can be damaged or cause a short. It is never cut, and coiling it around a control handle can interfere with the coupling mechanism.

Question 35Coupling and Uncoupling

You have coupled the tractor to the lead trailer of a triples set and completed a successful tug test. What should you do next before backing under the second trailer?

  1. Lower the lead trailer's landing gear to stabilize it
  2. Release the tractor's parking brake
  3. Disconnect the dolly from the lead trailer
  4. Raise the lead trailer's landing gear and connect its air lines Correct answer.

Explanation

After a successful tug test, the landing gear is raised and the air lines and electrical cord are connected so the combination has a functioning brake and light system. The lead trailer must be fully coupled and supported before you move on to the next trailer. Lowering the gear or disconnecting the dolly would undo the coupling work.

Question 36Coupling and Uncoupling

What is the primary reason a converter dolly is equipped with its own spring brakes?

  1. To allow the dolly to be parked and held independently when uncoupled from the tractor Correct answer.
  2. To supply air to the second trailer's brake system
  3. To provide steering assist at low speed
  4. To increase the load capacity of the combination

Explanation

The dolly's spring brakes hold it stationary when it is uncoupled and parked, which is essential because the dolly has no landing gear. They also provide braking during normal operation. They do not increase load capacity, steer the dolly, or supply air to the trailer.

Question 37Coupling and Uncoupling

While coupling a second trailer to a dolly, you find the trailer's kingpin is too high and the fifth wheel jaws close on air. What is the most appropriate corrective action?

  1. Back under the trailer at a sharper angle to force the jaws closed
  2. Lower the trailer with the landing gear until the kingpin sits at the correct height, then recouple Correct answer.
  3. Pull forward and let the trailer drop onto the fifth wheel
  4. Release the dolly's spring brakes and try again

Explanation

If the kingpin is too high, the jaws close on air and the coupling is not secure. The trailer must be lowered with the landing gear until the kingpin is at the proper height, then the coupling is repeated and verified with a tug test. Forcing the jaws or dropping the trailer damages equipment and is unsafe.

Question 38Coupling and Uncoupling

You are uncoupling the rear trailer of a doubles set. The trailer's air lines are still connected and the trailer brakes are released. What is the risk of disconnecting the glad hands in this condition?

  1. The dolly will lift off the ground
  2. The electrical cord will short out
  3. The glad hands will not release because of pressure
  4. The trailer brakes will apply automatically and the trailer may roll Correct answer.

Explanation

If the trailer brakes are released and the lines are disconnected, the trailer loses its air supply and the spring brakes apply, which can cause the trailer to lurch or roll if it is not chocked. The correct procedure is to set the trailer brakes and chock the wheels before disconnecting the lines. The other outcomes are not the primary hazard.

Question 39Coupling and Uncoupling

What should you check about the dolly's fifth wheel locking lever before backing the dolly under a trailer?

  1. That it is removed entirely
  2. That it is wired open
  3. That it is in the locked position so the fifth wheel stays level Correct answer.
  4. That it is in the unlocked position so the jaws can open

Explanation

The locking lever must be in the locked position so the fifth wheel plate stays level and the jaws can capture the kingpin. If the lever is unlocked, the plate can tip and the coupling will fail. The lever is not removed or wired open during coupling.

Question 40Coupling and Uncoupling

After uncoupling a dolly from the lead trailer, where should the dolly's air lines be placed?

  1. Tucked under the dolly's tires
  2. Draped over the dolly frame with the glad hands secured so they do not drag Correct answer.
  3. Connected to each other to form a loop
  4. Left hanging so they can be grabbed quickly for the next coupling

Explanation

Air lines should be secured so the glad hands do not drag on the ground or get damaged, and so they are ready for the next coupling. Leaving them hanging risks damage, and placing them under the tires damages the lines and can affect the dolly's stability. Connecting them to each other is not the standard practice for stowing dolly lines.

Question 41Pulling Double/Triple Trailers and Inspecting the Combination

When coupling a tractor to the first semitrailer, what is the correct order of steps before you back under the trailer?

  1. Raise the fifth wheel plate and close the jaws so the kingpin slides in freely
  2. Lock the trailer brakes and release the tractor spring brakes so the tractor can roll
  3. Lower the landing gear fully and connect the air lines before backing under
  4. Check the fifth wheel jaws are open, the trailer kingpin is high enough, and the trailer wheels are chocked Correct answer.

Explanation

Before backing under, the fifth wheel must be tilted down with jaws open and the locking lever in the open position, the trailer must be raised or lowered so the kingpin will clear the fifth wheel plate, and the trailer wheels must be chocked to prevent it from rolling. Air lines and electrical cords are connected after the tractor is under the trailer and the kingpin is locked.

Question 42Pulling Double/Triple Trailers and Inspecting the Combination

After the fifth wheel jaws close on the kingpin, how do you confirm the coupling is secure?

  1. Listen for the air dryer to purge, which signals a completed coupling
  2. Watch the trailer nose rise slightly as you back under and assume the lock engaged
  3. Release the trailer spring brakes and let the combination roll a few feet
  4. Pull the tractor forward gently against the locked trailer brakes and check that the jaws are closed around the kingpin Correct answer.

Explanation

A pull test with the trailer brakes set confirms the jaws are locked around the kingpin; if the coupling is incomplete the trailer will not move with the tractor or the tractor will pull out from under it. Visually checking that the jaws are closed and the release lever is in the locked position is also required. Listening for the tractor air dryer or relying on trailer movement alone does not verify the lock.

Question 43Pulling Double/Triple Trailers and Inspecting the Combination

Which combination of air line connections is correct when hooking a tractor to a semitrailer?

  1. Both lines to the emergency gladhand using a Y-fitting so either can supply the trailer
  2. Emergency (supply) line to the emergency gladhand and service line to the service gladhand, matched by color Correct answer.
  3. Emergency line to the service gladhand and service line to the emergency gladhand, crossed to balance pressure
  4. Emergency line only; the service line is used solely when pulling doubles

Explanation

The emergency (supply) line charges the trailer air tanks and applies the trailer spring brakes when pressure is lost, while the service line carries the brake application signal from the foot valve. Gladhands are color-coded and must be matched correctly; crossing them causes brake malfunction. Both lines are required on every air-braked trailer.

Question 44Pulling Double/Triple Trailers and Inspecting the Combination

What is the function of the converter dolly in a doubles or triples combination?

  1. It carries the kingpin of the second trailer and transmits the load to the tractor frame
  2. It boosts air pressure between the tractor and the rear trailers
  3. It converts the first semitrailer into a full trailer by providing a fifth wheel and axle set Correct answer.
  4. It links the electrical systems of the trailers into one circuit

Explanation

A converter dolly is a small frame with one or two axles, a fifth wheel, and a drawbar; it attaches to the rear of the first semitrailer so a second semitrailer can be coupled like a full trailer. It does not carry trailer load to the tractor frame, generate air pressure, or combine electrical circuits.

Question 45Pulling Double/Triple Trailers and Inspecting the Combination

Which statement about the shut-off valves (trailer air supply valves) on a converter dolly is correct?

  1. They are only used to drain moisture from the dolly tanks
  2. They must be open at all times so the dolly tanks stay charged
  3. They must be closed when the dolly is towed without a rear trailer to prevent air loss Correct answer.
  4. They regulate the amount of air pressure sent to the rear trailer brakes

Explanation

Shut-off valves on the dolly control air flow to the rear trailer's lines; when the dolly is towed bobtail or without a rear trailer, closing them prevents air from escaping through open gladhands. They do not regulate brake pressure or serve as drain valves, and leaving them open with no trailer attached wastes air.

Question 46Pulling Double/Triple Trailers and Inspecting the Combination

A driver is inspecting the coupling between the first semitrailer and the converter dolly. Which check is most important?

  1. That the dolly fifth wheel jaws are locked on the first trailer's kingpin and the release lever is secured Correct answer.
  2. That the dolly drawbar is secured with the safety chains crossed under the drawbar
  3. That the dolly air tanks are fully drained before each trip
  4. That the dolly tires are inflated to the tractor steer tire pressure

Explanation

The critical coupling in a doubles setup is between the first trailer's rear kingpin and the dolly's fifth wheel; the jaws must be locked and the release handle secured so the dolly cannot separate. Safety chains are used on the rear trailer connection, tire pressures follow the dolly manufacturer's specification, and tanks should be charged, not drained.

Question 47Pulling Double/Triple Trailers and Inspecting the Combination

When inspecting a triple trailer combination, why must you check the gladhands and air lines at every connection point?

  1. Air line inspection is only required when the combination exceeds two trailers
  2. Only the front connection matters because the rear lines are isolated by check valves
  3. Each connection is a potential leak or disconnect that can apply the spring brakes or cause a loss of control Correct answer.
  4. Gladhand couplers automatically seal, so only the tractor connection requires inspection

Explanation

In a multi-trailer combination every gladhand pair and air line is a possible leak source or separation point; a disconnected supply line will set the spring brakes and a service line leak can delay or weaken braking. Check valves protect against some loss but do not eliminate the need to inspect each coupling. The requirement applies to doubles as well as triples.

Question 48Pulling Double/Triple Trailers and Inspecting the Combination

How does a combination with two or three trailers typically behave in a turn compared with a single semitrailer?

  1. The rear trailers track outside the tractor path, so you must steer closer to the curb
  2. The combination turns in the same path as a single trailer regardless of length
  3. The rear trailers cut the corner sharply, so you must slow and hug the inside line
  4. The rear trailers track farther inside the turn, so you must swing wider to keep them off the curb Correct answer.

Explanation

Each additional trailer off-tracks toward the inside of the turn, so the last trailer in a triple cuts the corner more than the first. Drivers must swing wider and watch the rear trailer in mirrors to avoid hitting curbs, poles, or other vehicles. The effect is exaggerated, not eliminated, as trailers are added.

Question 49Pulling Double/Triple Trailers and Inspecting the Combination

What is the safest way to back a doubles or triples combination?

  1. Back only the rear trailer by unlocking the dolly fifth wheel first
  2. Avoid backing whenever possible and plan the route so you can pull forward instead Correct answer.
  3. Back slowly with a spotter at the rear trailer and use mirrors continuously
  4. Back at normal speed to keep the trailers from jackknifing

Explanation

Multi-trailer combinations are extremely difficult to back because each articulation point reverses steering response; the standard guidance is to avoid backing and plan ahead. When backing is unavoidable, use a spotter and go very slowly, but the primary rule is to minimize it. Unlocking the dolly fifth wheel while backing is unsafe.

Question 50Pulling Double/Triple Trailers and Inspecting the Combination

A driver must make a lane change with a triple trailer combination. What is the key consideration?

  1. Change lanes without signaling because the trailers block the view of other drivers
  2. Change lanes quickly so the rear trailers do not drift
  3. Signal early, check mirrors for the full length of the combination, and allow extra time to complete the move Correct answer.
  4. Rely on the convex mirror only because the rear trailers are far behind

Explanation

A multi-trailer combination is long and slow to clear a lane; you must signal early, verify all trailers are clear using flat and convex mirrors, and complete the move smoothly. Quick lane changes increase the risk of trailer sway and off-tracking into the adjacent lane. Signaling is always required.